When stretching is worthwhile
Lighter paper often buckles with generous washes. If you plan to work very wet or need a perfectly flat surface, stretching it first saves later corrections.
The tape method
Dampen the back of the sheet evenly, place it on a clean board and secure all four edges with gummed tape or watercolor-safe tape. Let it dry completely and paint without removing it.
A simpler alternative
With 300 gsm paper, a rigid board and low-tack tape are usually enough for studies and exercises. Avoid removing the sheet while it is wet; wait until both paper and paint are dry.
Choose a rigid support
A smooth, clean board slightly larger than the sheet lets you move the work without touching the paper. Avoid surfaces that transfer ink, dust or texture when damp.
Control moisture
The paper should be evenly damp, not soaked. If puddles appear, remove them with a clean sponge before fixing the edges so drying stays even.
Secure without over-tensioning
Apply the tape along the edge and press it gently. Pulling the paper too much can distort it; tension should develop naturally as it dries.
Remove slowly
When the work is completely dry, cut the tape at the edge with a clean blade or peel it slowly parallel to the surface. This preserves a clean margin.